Add logging for legacy private dataset access

[snwessel]

Asana

Adding logging to confirm private datasets are only being read from breadbox after their migration. This makes use of the existing data_access logging which writes to a access.log file. These logs will be written as their own unique "type" so they'll be easy to search for:

{"timestamp": "2024-07-22T13:04:39.565780", "type": "legacy-private-dataset-access", "endpoint": "data_explorer_2.plot_dimensions", "function": "compute_dimension", "dataset": "d6196b18-b1f8-4646-a182-9c8c29950fbf", "user": "[email protected]"}

I didn't want to be super repetitive about updating the codebase to check "if it's a private dataset, write a log", so I just updated a couple of low-level frequently used functions like get_dataset_label to log whenever they're called with a non-breadbox private dataset.

[pgm]

LGTM